Various additives are proposed for the purpose of improving the photographic characteristics (sensitivity, fog and rapid development performance) of a silver halide light-sensitive material.
The addition of the hydrazine compounds to a silver halide emulsion and a developing solution is disclosed in U.S. Pat. Nos. 3,730,727 (a developing solution in which ascorbic acid and hydrazine are combined), 3,227,552 (hydrazine is used as an auxiliary developing agent for obtaining a direct positive color image), 3,386,831 (.beta.-mono-phenylhydrazide of aliphatic carboxylic acid is contained as a stabilizer for a silver halide light-sensitive material), and 2,419,975, and The Theory of Photographic Process written by Mees, the third edition (1966), p. 281.
Among them, in particular, it is disclosed in U.S. Pat. No. 2,419,975 that the addition of a hydrazine compound can provide a negative image with a high contrast.
It is described in the specification of the above patent that the addition of the hydrazine compound to a silver bromochloride emulsion and development in a developing solution of pH as high as 12.8 can provide a photographic characteristic with a very high contrast having gamma (.gamma.) exceeding 10. However, a strongly alkaline developing solution is susceptible to air oxidation and is unstable. Accordingly, it is not durable in storage and use over a long time.
Methods have been attempted in which a silver halide light-sensitive material containing a hydrazine compound is developed in a developing solution of lower pH to form an image with a high contrast.
There are proposed in JP-A-1-179939 (the term "JP-A" as used herein means an unexamined published Japanese patent application) and 1-179940, processing methods in which a light-sensitive material containing a nucleus-forming development accelerator having an adsorbing group to silver halide emulsion grains and a nucleus-forming agent having an adsorbing group is developed in a developing solution of a pH 11 or lower. However, the compound having an adsorbing group has the defect that when it is added to a silver halide emulsion, the amount thereof exceeding certain limit deteriorates light sensitivity and inhibits a development or that it prevents the action of other more useful adsorptive additives. Accordingly, a sufficiently high contrast performance thereof can not be obtained since the use amount thereof is limited.
It is disclosed in JP-A-60-14030 that amines are added to a silver halide light-sensitive material increase in high contrast. However, in the case where development is carried out in a developing solution with a pH lower than 11.0, a sufficient high contrast can not be obtained.
It is disclosed in JP-A-56-106244 that an amino compound is added to a developing solution of a pH 10 to 12 to increase contrast. However, in the case where amines are added to the developing solution, there are the problems of odor of the solution, stain due to sticking thereof to the equipment used, and environmental pollution attributable to the waste solution. Those amines which are desired to be incorporated into a light-sensitive material and are actually added to provide sufficient performance have not yet been found.
There are disclosed in U.S. Pat. Nos. 4,998,604 and 4,994,365, hydrazine compounds having a recurring unit of ethylene oxide and hydrazine compounds having a pyridinium group. However, as is apparent from the examples, the high contrast is not sufficient and it is difficult to obtain high contrast and needed Dmax under practicable development processing conditions.
A nucleus-forming high contrast light-sensitive material in which a hydrazine derivative is used has a large fluctuation range of photographic performance according to changes in the pH of the developing solution. The pH value of the developing solution goes up due to air oxidation of the developing solution and the concentration thereof caused by the evaporation of water, and it is lowered due to the absorption of carbon dioxide in air, so that it is changed to a large extent. Accordingly, there is a need for a method to reduce the developing solution pH dependency of the photographic performance. Image quality which shows a sufficient high contrast and is good enough even with a processing by a developing solution having a pH of 11 or lower has not yet been obtained with conventional techniques.